Abstract
Vitrification has attracted much attention as an efficient method for solidifying heavy metals in hazardous solid wastes, but its effect is limited when hazardous solid wastes contain chlorides. Aiming at fly ash, a normal chlorine-containing solid waste, a novel process of chlorination melting and glass curing was developed to completely realize the harmlessness of heavy metals. Melting temperature, time, and auxiliary agent were adequate to realize the harmlessness, and their influence on the migration and transformation of Cl, Na, Pb, and Zn and the leaching of slag were studied. The results showed that the majority of Cl, Na, Pb, and Zn in the fly ash had been transferred to the soot, and the residual part in the slag had been solidified in glass by controlling the process conditions. Under the optimized conditions (12 wt.% CaO and 5 wt.% SiO2 was added, the N2 flow ratio was at 1 L/min, and the melting temperature was 1300 °C for 2 h), the leaching index was determined, including the acid dissolution ratio, the Pb and Zn content of the water leaching solution, and the acid leaching solution, which all met the requirements of the relevant standards. Furthermore, the novel process provided a simple and efficient approach for the disposal of other similar solid wastes containing chlorides and heavy metals.
Highlights
A large amount of solid waste produced in industrial production and urban life has caused severe environmental and geological hazards and waste of land resources.The treatment, disposal, and utilization of solid waste, especially hazardous solid waste, has always been the key to restricting the construction of environmental protection and ecological civilizations in various countries [1,2]
Fly ash was used as a test raw material from an incineration plant for the treatment Fly ash was used as a test raw material from an incineration plant for the treatment of hazardous wastes, which used a rotary furnace incineration process in the temperature of hazardous wastes, which used a rotary furnace incineration process in the temperature range of 800 °C–950
The slag ratio referred ferred to the weight ratio of the slag to the raw material after the reaction, and the burning to the weight ratio of the slag to the raw material after the reaction, and the burning loss ratio referred to the weight proportion of the substance transferred to the smoke and dust to the raw material after the chlorination and melting process
Summary
A large amount of solid waste produced in industrial production and urban life has caused severe environmental and geological hazards and waste of land resources. Unlike some studies aimed at inhibiting the chlorination reaction during the vitrification process, the novel process proposed in this research, as shown, utilized the chlorine contained by fly ash itself and controlled technical conditions to promote the chlorination reaction In this way, most heavy metals enter the soot to achieve enrichment, which allowed the comprehensive utilization of resources such as some industrialized projects [16,17]. To investigate the feasibility of the new process, fly ash chlorination volatilization tests and slag toxicity leaching tests were conducted under different conditions to investigate the migration, material phase conversion, and leaching behavior characteristics of Cl, Na, Pb, and Zn in fly ash These works all revolve around the realization of environmental harmlessness of solid waste after chlorination and vitrification.
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